(A) Field of the Invention
The present invention relates to a transparent substrate with optical compensation ability, and a liquid crystal display (LCD) using the same, and more particularly, to a transparent substrate with adjustable optical compensation ability of negative type c-plate phase difference and a liquid crystal display using the same.
(B) Description of the Related Art
The flexible display has become a new trend in the development of a new generation of displays because it has the following excellent properties: lightness, thinness, impact-resistance, not frangible, portability, bendability, ability to be rolled, wearability and greatly reduced cost due to continuous production in roll-to-roll. In order to meet the stringent process requirements of the active thin film transistor (TFT), the development of flexible substrate materials with high thermal resistance, low thermal coefficient of thermal expansion (CTE) and high chemical resistance will be a key factor in the development of a new generation of flexible display products.
The current optical plastic substrate materials including polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), and m-COC (Arton or Zeonor) cannot be adapted to the stringent process of the active TFT because the processing temperature will be limited by the glass transition temperatures (Tg) thereof, which are below 200° C., even though they are commercially available. The glass transition temperature of polyether sulfone (PES) is as high as 225° C.; however, it possesses a poor solvent-resistance and brittle cracking may occur over periods of high temperature (200° C.) operation.
The current polyimide plastic substrate with high temperature resistance and solvent resistance may meet current high-temperature processing requirements. However, it is useful only in reflective liquid crystal display panels, rather than transmissive liquid crystal display panels, due to its puce color. In addition, liquid crystal displays use the optical activity of liquid crystal molecules incorporating two polarization plates to show light and dark. However, the liquid crystal molecule has the birefringence property, and optical leakage frequently occurs when it is used in display panels, which results in such problems as limited viewing angle and poor contrast. Furthermore, the simplest method to obtain a wide viewing angle and increased contrast involves adhering an optical compensation film outside, which results in not only increased production cost but also increasing complexity in production of flexible liquid crystal displays.